title: Inhibitory mechanisms of dihydroginsenoside Rg3 in platelet aggregation: critical roles of ERK2 and cAMP.
abstract: Ginsenoside Rg3, a single ginseng saponin, is known to be a major anti-platelet component of protopanaxadiol that is isolated from Korean red ginseng. In this study, we investigated whether dihydroginsenoside Rg3, a stable chemical derivative of ginsenoside Rg3, also demonstrated anti-platelet activity. Dihydroginsenoside Rg3 inhibited thrombin-induced platelet aggregation in a concentration-dependent manner with an IC50 (concentration producing 50% inhibition) of 18.8 +/- 0.4 microM. Ginsenoside Rg3 inhibited platelet aggregation which was induced by thrombin (0.1 U mL(-1)) with an IC50 of 40.2 +/- 0.9 microM. We next determined whether dihydroginsenoside Rg3 affected different types of ligand-induced platelet aggregation. We found that dihydroginsenoside Rg3 inhibited collagen-induced platelet aggregation with an IC50 of 20.0 +/- 0.9 microM. To elucidate the inhibitory mechanism of dihydroginsenoside Rg3 on aggregation, we analysed its downstream signalling pathway. It was interesting to note that dihydroginsenoside Rg3 elevated cyclic AMP production in resting platelets, but did not affect cyclic GMP production. In addition, we found that dihydroginsenoside Rg3 potently suppressed phosphorylation of extracellular signal-regulated kinase 2 (ERK2), which was stimulated by collagen (2.5 microg mL(-1)), but not of p38 mitogen-activated protein kinase. Taken together, our results indicate that dihydroginsenoside Rg3 potently inhibited platelet aggregation via the modulation of downstream signalling components such as cAMP and ERK2.
authors.affiliation: Laboratory of Veterinary Physiology & Signaling, College of Veterinary Medicine, Kyungpook National University, Daegu 702-701, Korea.
authors.forename: Whi Min
authors.initials: WM
authors.lastname: Lee
authors.forename: Sung Dae
authors.initials: SD
authors.lastname: Kim
authors.forename: Myung Hwan
authors.initials: MH
authors.lastname: Park
authors.forename: Jae Youl
authors.initials: JY
authors.lastname: Cho
authors.forename: Hwa Jin
authors.initials: HJ
authors.lastname: Park
authors.forename: Geon Sik
authors.initials: GS
authors.lastname: Seo
authors.forename: Man Hee
authors.initials: MH
authors.lastname: Rhee
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D036145:Ginsenosides / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects* / Q000378:metabolism; D005894:Panax / Q000737:chemistry; D010766:Phosphorylation / Q000187:drug effects; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013917:Thrombin / Q000378:metabolism
chemical_list: D036145:Ginsenosides; D010975:Platelet Aggregation Inhibitors; C533909:dihydroginsenoside Rg3; D003094:Collagen; D000242:Cyclic AMP; D019950:Mitogen-Activated Protein Kinase 1; D013917:Thrombin